Revamp the SourceManager to separate the representation of parsed

source locations from source locations loaded from an AST/PCH file.

Previously, loading an AST/PCH file involved carefully pre-allocating
space at the beginning of the source manager for the source locations
and FileIDs that correspond to the prefix, and then appending the
source locations/FileIDs used for parsing the remaining translation
unit. This design forced us into loading PCH files early, as a prefix,
whic has become a rather significant limitation.

This patch splits the SourceManager space into two parts: for source
location "addresses", the lower values (growing upward) are used to
describe parsed code, while upper values (growing downward) are used
for source locations loaded from AST/PCH files. Similarly, positive
FileIDs are used to describe parsed code while negative FileIDs are
used to file/macro locations loaded from AST/PCH files. As a result,
we can load PCH/AST files even during parsing, making various
improvemnts in the future possible, e.g., teaching #include <foo.h> to
look for and load <foo.h.gch> if it happens to be already available.

This patch was originally written by Sebastian Redl, then brought
forward to the modern age by Jonathan Turner, and finally
polished/finished by me to be committed.

llvm-svn: 135484

2 files changed, 240 insertions, 136 deletions

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index a4ed5f4da48..61c3a5c2ff4 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -49,6 +49,7 @@
 #include <iterator>
 #include <cstdio>
 #include <sys/stat.h>
+#include <iostream>
 
 using namespace clang;
 using namespace clang::serialization;
@@ -1010,6 +1011,9 @@ bool ASTReader::ParseLineTable(PerFileData &F,
   std::vector<LineEntry> Entries;
   while (Idx < Record.size()) {
     int FID = Record[Idx++];
+    assert(FID >= 0 && "Serialized line entries for non-local file.");
+    // Remap FileID from 1-based old view.
+    FID += F.SLocEntryBaseID - 1;
 
     // Extract the line entries
     unsigned NumEntries = Record[Idx++];
@@ -1188,11 +1192,6 @@ ASTReader::ASTReadResult ASTReader::ReadSourceManagerBlock(PerFileData &F) {
     default:  // Default behavior: ignore.
       break;
 
-    case SM_LINE_TABLE:
-      if (ParseLineTable(F, Record))
-        return Failure;
-      break;
-
     case SM_SLOC_FILE_ENTRY:
     case SM_SLOC_BUFFER_ENTRY:
     case SM_SLOC_EXPANSION_ENTRY:
@@ -1235,38 +1234,20 @@ resolveFileRelativeToOriginalDir(const std::string &Filename,
   return currPCHPath.str();
 }
 
-/// \brief Get a cursor that's correctly positioned for reading the source
-/// location entry with the given ID.
-ASTReader::PerFileData *ASTReader::SLocCursorForID(unsigned ID) {
-  assert(ID != 0 && ID <= TotalNumSLocEntries &&
-         "SLocCursorForID should only be called for real IDs.");
-
-  ID -= 1;
-  PerFileData *F = 0;
-  for (unsigned I = 0, N = Chain.size(); I != N; ++I) {
-    F = Chain[N - I - 1];
-    if (ID < F->LocalNumSLocEntries)
-      break;
-    ID -= F->LocalNumSLocEntries;
-  }
-  assert(F && F->LocalNumSLocEntries > ID && "Chain corrupted");
-
-  F->SLocEntryCursor.JumpToBit(F->SLocOffsets[ID]);
-  return F;
-}
-
 /// \brief Read in the source location entry with the given ID.
-ASTReader::ASTReadResult ASTReader::ReadSLocEntryRecord(unsigned ID) {
+ASTReader::ASTReadResult ASTReader::ReadSLocEntryRecord(int ID) {
   if (ID == 0)
     return Success;
 
-  if (ID > TotalNumSLocEntries) {
+  if (unsigned(-ID) - 2 >= TotalNumSLocEntries || ID > 0) {
     Error("source location entry ID out-of-range for AST file");
     return Failure;
   }
 
-  PerFileData *F = SLocCursorForID(ID);
+  PerFileData *F = GlobalSLocEntryMap.find(-ID)->second;
+  F->SLocEntryCursor.JumpToBit(F->SLocEntryOffsets[ID - F->SLocEntryBaseID]);
   llvm::BitstreamCursor &SLocEntryCursor = F->SLocEntryCursor;
+  unsigned BaseOffset = F->SLocEntryBaseOffset;
 
   ++NumSLocEntriesRead;
   unsigned Code = SLocEntryCursor.ReadCode();
@@ -1326,9 +1307,14 @@ ASTReader::ASTReadResult ASTReader::ReadSLocEntryRecord(unsigned ID) {
       return Failure;
     }
 
-    FileID FID = SourceMgr.createFileID(File, ReadSourceLocation(*F, Record[1]),
+    SourceLocation IncludeLoc = ReadSourceLocation(*F, Record[1]);
+    if (IncludeLoc.isInvalid() && F->Type != MainFile) {
+      // This is the module's main file.
+      IncludeLoc = getImportLocation(F);
+    }
+    FileID FID = SourceMgr.createFileID(File, IncludeLoc,
                                         (SrcMgr::CharacteristicKind)Record[2],
-                                        ID, Record[0]);
+                                        ID, BaseOffset + Record[0]);
     if (Record[3])
       const_cast<SrcMgr::FileInfo&>(SourceMgr.getSLocEntry(FID).getFile())
         .setHasLineDirectives();
@@ -1352,7 +1338,8 @@ ASTReader::ASTReadResult ASTReader::ReadSLocEntryRecord(unsigned ID) {
     llvm::MemoryBuffer *Buffer
     = llvm::MemoryBuffer::getMemBuffer(llvm::StringRef(BlobStart, BlobLen - 1),
                                        Name);
-    FileID BufferID = SourceMgr.createFileIDForMemBuffer(Buffer, ID, Offset);
+    FileID BufferID = SourceMgr.createFileIDForMemBuffer(Buffer, ID,
+                                                         BaseOffset + Offset);
 
     if (strcmp(Name, "<built-in>") == 0) {
       PCHPredefinesBlock Block = {
@@ -1372,7 +1359,7 @@ ASTReader::ASTReadResult ASTReader::ReadSLocEntryRecord(unsigned ID) {
                                      ReadSourceLocation(*F, Record[3]),
                                      Record[4],
                                      ID,
-                                     Record[0]);
+                                     BaseOffset + Record[0]);
     break;
   }
   }
@@ -1380,6 +1367,23 @@ ASTReader::ASTReadResult ASTReader::ReadSLocEntryRecord(unsigned ID) {
   return Success;
 }
 
+/// \brief Find the location where the module F is imported.
+SourceLocation ASTReader::getImportLocation(PerFileData *F) {
+  if (F->ImportLoc.isValid())
+    return F->ImportLoc;
+  // Otherwise we have a PCH. It's considered to be "imported" at the first
+  // location of its includer.
+  if (F->Loaders.empty() || !F->Loaders[0]) {
+    // Main file is the importer. We assume that it is the first entry in the
+    // entry table. We can't ask the manager, because at the time of PCH loading
+    // the main file entry doesn't exist yet.
+    // The very first entry is the invalid instantiation loc, which takes up
+    // offsets 0 and 1.
+    return SourceLocation::getFromRawEncoding(2U);
+  }
+  return F->Loaders[0]->FirstLoc;
+}
+
 /// ReadBlockAbbrevs - Enter a subblock of the specified BlockID with the
 /// specified cursor.  Read the abbreviations that are at the top of the block
 /// and then leave the cursor pointing into the block.
@@ -2191,10 +2195,53 @@ ASTReader::ReadASTBlock(PerFileData &F) {
         Listener->ReadCounter(Record[0]);
       break;
 
-    case SOURCE_LOCATION_OFFSETS:
-      F.SLocOffsets = (const uint32_t *)BlobStart;
+    case SOURCE_LOCATION_OFFSETS: {
+      F.SLocEntryOffsets = (const uint32_t *)BlobStart;
       F.LocalNumSLocEntries = Record[0];
-      F.LocalSLocSize = Record[1];
+      llvm::tie(F.SLocEntryBaseID, F.SLocEntryBaseOffset) =
+          SourceMgr.AllocateLoadedSLocEntries(F.LocalNumSLocEntries, Record[1]);
+      // Make our entry in the range map. BaseID is negative and growing, so
+      // we invert it. Because we invert it, though, we need the other end of
+      // the range.
+      unsigned RangeStart =
+          unsigned(-F.SLocEntryBaseID) - F.LocalNumSLocEntries + 1;
+      GlobalSLocEntryMap.insert(std::make_pair(RangeStart, &F));
+      F.FirstLoc = SourceLocation::getFromRawEncoding(F.SLocEntryBaseOffset);
+
+      // Initialize the remapping table.
+      // Invalid stays invalid.
+      F.SLocRemap.insert(std::make_pair(0U, 0));
+      // This module. Base was 2 when being compiled.
+      F.SLocRemap.insert(std::make_pair(2U,
+                                  static_cast<int>(F.SLocEntryBaseOffset - 2)));
+      break;
+    }
+
+    case SOURCE_LOCATION_MAP: {
+      // Additional remapping information.
+      const unsigned char *Data = (const unsigned char*)BlobStart;
+      const unsigned char *DataEnd = Data + BlobLen;
+      while(Data < DataEnd) {
+        uint32_t Offset = io::ReadUnalignedLE32(Data);
+        uint16_t Len = io::ReadUnalignedLE16(Data);
+        llvm::StringRef Name = llvm::StringRef((const char*)Data, Len);
+        PerFileData *OM = Modules.lookup(Name);
+        if (!OM) {
+          Error("SourceLocation remap refers to unknown module");
+          return Failure;
+        }
+        // My Offset is mapped to OM->SLocEntryBaseOffset.
+        F.SLocRemap.insert(std::make_pair(Offset,
+                        static_cast<int>(OM->SLocEntryBaseOffset - Offset)));
+        Data += Len;
+      }
+      break;
+    }
+
+
+    case SOURCE_MANAGER_LINE_TABLE:
+      if (ParseLineTable(F, Record))
+        return Failure;
       break;
 
     case FILE_SOURCE_LOCATION_OFFSETS:
@@ -2202,13 +2249,14 @@ ASTReader::ReadASTBlock(PerFileData &F) {
       F.LocalNumSLocFileEntries = Record[0];
       break;
 
-    case SOURCE_LOCATION_PRELOADS:
-      if (PreloadSLocEntries.empty())
-        PreloadSLocEntries.swap(Record);
-      else
-        PreloadSLocEntries.insert(PreloadSLocEntries.end(),
-            Record.begin(), Record.end());
+    case SOURCE_LOCATION_PRELOADS: {
+      // Need to transform from the local view (1-based IDs) to the global view,
+      // which is based off F.SLocEntryBaseID.
+      PreloadSLocEntries.reserve(PreloadSLocEntries.size() + Record.size());
+      for (unsigned I = 0, N = Record.size(); I != N; ++I)
+        PreloadSLocEntries.push_back(int(Record[I] - 1) + F.SLocEntryBaseID);
       break;
+    }
 
     case STAT_CACHE: {
       if (!DisableStatCache) {
@@ -2326,11 +2374,12 @@ ASTReader::ReadASTBlock(PerFileData &F) {
         Error("invalid DIAG_USER_MAPPINGS block in AST file");
         return Failure;
       }
-      if (PragmaDiagMappings.empty())
-        PragmaDiagMappings.swap(Record);
+        
+      if (F.PragmaDiagMappings.empty())
+        F.PragmaDiagMappings.swap(Record);
       else
-        PragmaDiagMappings.insert(PragmaDiagMappings.end(),
-                                Record.begin(), Record.end());
+        F.PragmaDiagMappings.insert(F.PragmaDiagMappings.end(),
+                                    Record.begin(), Record.end());
       break;
         
     case CUDA_SPECIAL_DECL_REFS:
@@ -2478,7 +2527,6 @@ ASTReader::ASTReadResult ASTReader::ReadAST(const std::string &FileName,
            TotalNumSelectors = 0;
   for (unsigned I = 0, N = Chain.size(); I != N; ++I) {
     TotalNumSLocEntries += Chain[I]->LocalNumSLocEntries;
-    NextSLocOffset += Chain[I]->LocalSLocSize;
     TotalNumIdentifiers += Chain[I]->LocalNumIdentifiers;
     TotalNumTypes += Chain[I]->LocalNumTypes;
     TotalNumDecls += Chain[I]->LocalNumDecls;
@@ -2487,7 +2535,6 @@ ASTReader::ASTReadResult ASTReader::ReadAST(const std::string &FileName,
     TotalNumMacroDefs += Chain[I]->LocalNumMacroDefinitions;
     TotalNumSelectors += Chain[I]->LocalNumSelectors;
   }
-  SourceMgr.PreallocateSLocEntries(this, TotalNumSLocEntries, NextSLocOffset);
   IdentifiersLoaded.resize(TotalNumIdentifiers);
   TypesLoaded.resize(TotalNumTypes);
   DeclsLoaded.resize(TotalNumDecls);
@@ -2507,7 +2554,7 @@ ASTReader::ASTReadResult ASTReader::ReadAST(const std::string &FileName,
   for (unsigned I = 0, N = PreloadSLocEntries.size(); I != N; ++I) {
     ASTReadResult Result = ReadSLocEntryRecord(PreloadSLocEntries[I]);
     if (Result != Success)
-      return Result;
+      return Failure;
   }
 
   // Check the predefines buffers.
@@ -2572,7 +2619,11 @@ ASTReader::ASTReadResult ASTReader::ReadAST(const std::string &FileName,
       if (Loc.isValid())
         OriginalFileID = SourceMgr.getDecomposedLoc(Loc).first;
     }
-    
+    else {
+      OriginalFileID = FileID::get(Chain[0]->SLocEntryBaseID 
+                                        + OriginalFileID.getOpaqueValue() - 1);
+    }
+
     if (!OriginalFileID.isInvalid())
       SourceMgr.SetPreambleFileID(OriginalFileID);
   }
@@ -2590,6 +2641,8 @@ ASTReader::ASTReadResult ASTReader::ReadASTCore(llvm::StringRef FileName,
   else
     FirstInSource = &F;
   F.Loaders.push_back(Prev);
+  // A non-module AST file's module name is $filename.
+  Modules["$" + FileName.str()] = &F;
 
   // Set the AST file name.
   F.FileName = FileName;
@@ -2668,9 +2721,8 @@ ASTReader::ASTReadResult ASTReader::ReadASTCore(llvm::StringRef FileName,
         // AST block, skipping subblocks, to see if there are other
         // AST blocks elsewhere.
 
-        // Clear out any preallocated source location entries, so that
-        // the source manager does not try to resolve them later.
-        SourceMgr.ClearPreallocatedSLocEntries();
+        // FIXME: We can't clear loaded slocentries anymore.
+        //SourceMgr.ClearPreallocatedSLocEntries();
 
         // Remove the stat cache.
         if (F.StatCache)
@@ -3062,21 +3114,25 @@ HeaderFileInfo ASTReader::GetHeaderFileInfo(const FileEntry *FE) {
 }
 
 void ASTReader::ReadPragmaDiagnosticMappings(Diagnostic &Diag) {
-  unsigned Idx = 0;
-  while (Idx < PragmaDiagMappings.size()) {
-    SourceLocation
-      Loc = SourceLocation::getFromRawEncoding(PragmaDiagMappings[Idx++]);
-    while (1) {
-      assert(Idx < PragmaDiagMappings.size() &&
-             "Invalid data, didn't find '-1' marking end of diag/map pairs");
-      if (Idx >= PragmaDiagMappings.size())
-        break; // Something is messed up but at least avoid infinite loop in
-               // release build.
-      unsigned DiagID = PragmaDiagMappings[Idx++];
-      if (DiagID == (unsigned)-1)
-        break; // no more diag/map pairs for this location.
-      diag::Mapping Map = (diag::Mapping)PragmaDiagMappings[Idx++];
-      Diag.setDiagnosticMapping(DiagID, Map, Loc);
+  for (unsigned I = 0, N = Chain.size(); I != N; ++I) {
+    PerFileData &F = *Chain[I];
+    unsigned Idx = 0;
+    while (Idx < F.PragmaDiagMappings.size()) {
+      SourceLocation Loc = ReadSourceLocation(F, F.PragmaDiagMappings[Idx++]);
+      while (1) {
+        assert(Idx < F.PragmaDiagMappings.size() &&
+               "Invalid data, didn't find '-1' marking end of diag/map pairs");
+        if (Idx >= F.PragmaDiagMappings.size()) {
+          break; // Something is messed up but at least avoid infinite loop in
+                 // release build.
+        }
+        unsigned DiagID = F.PragmaDiagMappings[Idx++];
+        if (DiagID == (unsigned)-1) {
+          break; // no more diag/map pairs for this location.
+        }
+        diag::Mapping Map = (diag::Mapping)F.PragmaDiagMappings[Idx++];
+        Diag.setDiagnosticMapping(DiagID, Map, Loc);
+      }
     }
   }
 }
@@ -4571,7 +4627,7 @@ IdentifierInfo *ASTReader::DecodeIdentifierInfo(unsigned ID) {
   return IdentifiersLoaded[ID];
 }
 
-bool ASTReader::ReadSLocEntry(unsigned ID) {
+bool ASTReader::ReadSLocEntry(int ID) {
   return ReadSLocEntryRecord(ID) != Success;
 }
 
@@ -5175,9 +5231,10 @@ ASTReader::ASTReader(Preprocessor &PP, ASTContext *Context,
   : Listener(new PCHValidator(PP, *this)), DeserializationListener(0),
     SourceMgr(PP.getSourceManager()), FileMgr(PP.getFileManager()),
     Diags(PP.getDiagnostics()), SemaObj(0), PP(&PP), Context(Context),
-    Consumer(0), isysroot(isysroot), DisableValidation(DisableValidation),
+    Consumer(0), FirstInSource(0), RelocatablePCH(false), isysroot(isysroot), 
+    DisableValidation(DisableValidation),
     DisableStatCache(DisableStatCache), NumStatHits(0), NumStatMisses(0), 
-    NumSLocEntriesRead(0), TotalNumSLocEntries(0), NextSLocOffset(0), 
+    NumSLocEntriesRead(0), TotalNumSLocEntries(0), 
     NumStatementsRead(0), TotalNumStatements(0), NumMacrosRead(0), 
     TotalNumMacros(0), NumSelectorsRead(0), NumMethodPoolEntriesRead(0), 
     NumMethodPoolMisses(0), TotalNumMethodPoolEntries(0), 
@@ -5185,24 +5242,25 @@ ASTReader::ASTReader(Preprocessor &PP, ASTContext *Context,
     NumVisibleDeclContextsRead(0), TotalVisibleDeclContexts(0), 
     NumCurrentElementsDeserializing(0) 
 {
-  RelocatablePCH = false;
+  SourceMgr.setExternalSLocEntrySource(this);
 }
 
 ASTReader::ASTReader(SourceManager &SourceMgr, FileManager &FileMgr,
                      Diagnostic &Diags, const char *isysroot,
                      bool DisableValidation, bool DisableStatCache)
   : DeserializationListener(0), SourceMgr(SourceMgr), FileMgr(FileMgr),
-    Diags(Diags), SemaObj(0), PP(0), Context(0), Consumer(0),
-    isysroot(isysroot), DisableValidation(DisableValidation), 
-    DisableStatCache(DisableStatCache), NumStatHits(0), NumStatMisses(0), 
-    NumSLocEntriesRead(0), TotalNumSLocEntries(0),
-    NextSLocOffset(0), NumStatementsRead(0), TotalNumStatements(0),
-    NumMacrosRead(0), TotalNumMacros(0), NumSelectorsRead(0),
-    NumMethodPoolEntriesRead(0), NumMethodPoolMisses(0),
+    Diags(Diags), SemaObj(0), PP(0), Context(0), Consumer(0), FirstInSource(0),
+    RelocatablePCH(false), isysroot(isysroot), 
+    DisableValidation(DisableValidation), DisableStatCache(DisableStatCache), 
+    NumStatHits(0), NumStatMisses(0), NumSLocEntriesRead(0), 
+    TotalNumSLocEntries(0), NumStatementsRead(0), 
+    TotalNumStatements(0), NumMacrosRead(0), TotalNumMacros(0), 
+    NumSelectorsRead(0), NumMethodPoolEntriesRead(0), NumMethodPoolMisses(0),
     TotalNumMethodPoolEntries(0), NumLexicalDeclContextsRead(0),
     TotalLexicalDeclContexts(0), NumVisibleDeclContextsRead(0),
-    TotalVisibleDeclContexts(0), NumCurrentElementsDeserializing(0) {
-  RelocatablePCH = false;
+    TotalVisibleDeclContexts(0), NumCurrentElementsDeserializing(0) 
+{
+  SourceMgr.setExternalSLocEntrySource(this);
 }
 
 ASTReader::~ASTReader() {
@@ -5231,13 +5289,13 @@ ASTReader::~ASTReader() {
 }
 
 ASTReader::PerFileData::PerFileData(ASTFileType Ty)
-  : Type(Ty), SizeInBits(0), LocalNumSLocEntries(0), SLocOffsets(0),
-    SLocFileOffsets(0), LocalSLocSize(0),
-    LocalNumIdentifiers(0), IdentifierOffsets(0), IdentifierTableData(0),
+  : Type(Ty), SizeInBits(0), LocalNumSLocEntries(0), SLocEntryBaseID(0),
+    SLocEntryBaseOffset(0), SLocEntryOffsets(0),
+    SLocFileOffsets(0), LocalNumIdentifiers(0), 
+    IdentifierOffsets(0), IdentifierTableData(0),
     IdentifierLookupTable(0), LocalNumMacroDefinitions(0),
-    MacroDefinitionOffsets(0), 
-    LocalNumHeaderFileInfos(0), HeaderFileInfoTableData(0),
-    HeaderFileInfoTable(0),
+    MacroDefinitionOffsets(0), LocalNumHeaderFileInfos(0), 
+    HeaderFileInfoTableData(0), HeaderFileInfoTable(0),
     LocalNumSelectors(0), SelectorOffsets(0),
     SelectorLookupTableData(0), SelectorLookupTable(0), LocalNumDecls(0),
     DeclOffsets(0), LocalNumCXXBaseSpecifiers(0), CXXBaseSpecifiersOffsets(0),
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 39f2fbddf80..a3a03a5b1f1 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -45,8 +45,10 @@
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
+#include <algorithm>
 #include <cstdio>
 #include <string.h>
+#include <utility>
 using namespace clang;
 using namespace clang::serialization;
 
@@ -790,7 +792,6 @@ void ASTWriter::WriteBlockInfoBlock() {
   RECORD(SM_SLOC_BUFFER_ENTRY);
   RECORD(SM_SLOC_BUFFER_BLOB);
   RECORD(SM_SLOC_EXPANSION_ENTRY);
-  RECORD(SM_LINE_TABLE);
 
   // Preprocessor Block.
   BLOCK(PREPROCESSOR_BLOCK);
@@ -1416,43 +1417,6 @@ void ASTWriter::WriteSourceManagerBlock(SourceManager &SourceMgr,
   unsigned SLocBufferBlobAbbrv = CreateSLocBufferBlobAbbrev(Stream);
   unsigned SLocExpansionAbbrv = CreateSLocExpansionAbbrev(Stream);
 
-  // Write the line table.
-  if (SourceMgr.hasLineTable()) {
-    LineTableInfo &LineTable = SourceMgr.getLineTable();
-
-    // Emit the file names
-    Record.push_back(LineTable.getNumFilenames());
-    for (unsigned I = 0, N = LineTable.getNumFilenames(); I != N; ++I) {
-      // Emit the file name
-      const char *Filename = LineTable.getFilename(I);
-      Filename = adjustFilenameForRelocatablePCH(Filename, isysroot);
-      unsigned FilenameLen = Filename? strlen(Filename) : 0;
-      Record.push_back(FilenameLen);
-      if (FilenameLen)
-        Record.insert(Record.end(), Filename, Filename + FilenameLen);
-    }
-
-    // Emit the line entries
-    for (LineTableInfo::iterator L = LineTable.begin(), LEnd = LineTable.end();
-         L != LEnd; ++L) {
-      // Emit the file ID
-      Record.push_back(L->first);
-
-      // Emit the line entries
-      Record.push_back(L->second.size());
-      for (std::vector<LineEntry>::iterator LE = L->second.begin(),
-                                         LEEnd = L->second.end();
-           LE != LEEnd; ++LE) {
-        Record.push_back(LE->FileOffset);
-        Record.push_back(LE->LineNo);
-        Record.push_back(LE->FilenameID);
-        Record.push_back((unsigned)LE->FileKind);
-        Record.push_back(LE->IncludeOffset);
-      }
-    }
-    Stream.EmitRecord(SM_LINE_TABLE, Record);
-  }
-
   // Write out the source location entry table. We skip the first
   // entry, which is always the same dummy entry.
   std::vector<uint32_t> SLocEntryOffsets;
@@ -1460,12 +1424,11 @@ void ASTWriter::WriteSourceManagerBlock(SourceManager &SourceMgr,
   // We will go through them in ASTReader::validateFileEntries().
   std::vector<uint32_t> SLocFileEntryOffsets;
   RecordData PreloadSLocs;
-  unsigned BaseSLocID = Chain ? Chain->getTotalNumSLocs() : 0;
-  SLocEntryOffsets.reserve(SourceMgr.sloc_entry_size() - 1 - BaseSLocID);
-  for (unsigned I = BaseSLocID + 1, N = SourceMgr.sloc_entry_size();
+  SLocEntryOffsets.reserve(SourceMgr.local_sloc_entry_size() - 1);
+  for (unsigned I = 1, N = SourceMgr.local_sloc_entry_size();
        I != N; ++I) {
     // Get this source location entry.
-    const SrcMgr::SLocEntry *SLoc = &SourceMgr.getSLocEntry(I);
+    const SrcMgr::SLocEntry *SLoc = &SourceMgr.getLocalSLocEntry(I);
 
     // Record the offset of this source-location entry.
     SLocEntryOffsets.push_back(Stream.GetCurrentBitNo());
@@ -1483,7 +1446,8 @@ void ASTWriter::WriteSourceManagerBlock(SourceManager &SourceMgr,
     Record.clear();
     Record.push_back(Code);
 
-    Record.push_back(SLoc->getOffset());
+    // Starting offset of this entry within this module, so skip the dummy.
+    Record.push_back(SLoc->getOffset() - 2);
     if (SLoc->isFile()) {
       const SrcMgr::FileInfo &File = SLoc->getFile();
       Record.push_back(File.getIncludeLoc().getRawEncoding());
@@ -1535,8 +1499,9 @@ void ASTWriter::WriteSourceManagerBlock(SourceManager &SourceMgr,
                                   llvm::StringRef(Buffer->getBufferStart(),
                                                   Buffer->getBufferSize() + 1));
 
-        if (strcmp(Name, "<built-in>") == 0)
-          PreloadSLocs.push_back(BaseSLocID + SLocEntryOffsets.size());
+        if (strcmp(Name, "<built-in>") == 0) {
+          PreloadSLocs.push_back(SLocEntryOffsets.size());
+        }
       }
     } else {
       // The source location entry is a macro expansion.
@@ -1546,9 +1511,9 @@ void ASTWriter::WriteSourceManagerBlock(SourceManager &SourceMgr,
       Record.push_back(Inst.getInstantiationLocEnd().getRawEncoding());
 
       // Compute the token length for this macro expansion.
-      unsigned NextOffset = SourceMgr.getNextOffset();
+      unsigned NextOffset = SourceMgr.getNextLocalOffset();
       if (I + 1 != N)
-        NextOffset = SourceMgr.getSLocEntry(I + 1).getOffset();
+        NextOffset = SourceMgr.getLocalSLocEntry(I + 1).getOffset();
       Record.push_back(NextOffset - SLoc->getOffset() - 1);
       Stream.EmitRecordWithAbbrev(SLocExpansionAbbrv, Record);
     }
@@ -1565,17 +1530,54 @@ void ASTWriter::WriteSourceManagerBlock(SourceManager &SourceMgr,
   BitCodeAbbrev *Abbrev = new BitCodeAbbrev();
   Abbrev->Add(BitCodeAbbrevOp(SOURCE_LOCATION_OFFSETS));
   Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 16)); // # of slocs
-  Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 16)); // next offset
+  Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 16)); // total size
   Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob)); // offsets
   unsigned SLocOffsetsAbbrev = Stream.EmitAbbrev(Abbrev);
 
   Record.clear();
   Record.push_back(SOURCE_LOCATION_OFFSETS);
   Record.push_back(SLocEntryOffsets.size());
-  unsigned BaseOffset = Chain ? Chain->getNextSLocOffset() : 0;
-  Record.push_back(SourceMgr.getNextOffset() - BaseOffset);
+  Record.push_back(SourceMgr.getNextLocalOffset() - 1); // skip dummy
   Stream.EmitRecordWithBlob(SLocOffsetsAbbrev, Record, data(SLocEntryOffsets));
 
+  // If we have module dependencies, write the mapping from source locations to
+  // their containing modules, so that the reader can build the remapping.
+  if (Chain) {
+    // The map consists solely of a blob with the following format:
+    // *(offset:i32 len:i16 name:len*i8)
+    // Sorted by offset.
+    typedef std::pair<uint32_t, llvm::StringRef> ModuleOffset;
+    llvm::SmallVector<ModuleOffset, 16> Modules;
+    Modules.reserve(Chain->Modules.size());
+    for (llvm::StringMap<ASTReader::PerFileData*>::const_iterator
+             I = Chain->Modules.begin(), E = Chain->Modules.end();
+         I != E; ++I) {
+      Modules.push_back(ModuleOffset(I->getValue()->SLocEntryBaseOffset,
+                                     I->getKey()));
+    }
+    std::sort(Modules.begin(), Modules.end());
+
+    Abbrev = new BitCodeAbbrev();
+    Abbrev->Add(BitCodeAbbrevOp(SOURCE_LOCATION_MAP));
+    Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob));
+    unsigned SLocMapAbbrev = Stream.EmitAbbrev(Abbrev);
+    llvm::SmallString<2048> Buffer;
+    {
+      llvm::raw_svector_ostream Out(Buffer);
+      for (llvm::SmallVector<ModuleOffset, 16>::iterator I = Modules.begin(),
+                                                         E = Modules.end();
+           I != E; ++I) {
+        io::Emit32(Out, I->first);
+        io::Emit16(Out, I->second.size());
+        Out.write(I->second.data(), I->second.size());
+      }
+    }
+    Record.clear();
+    Record.push_back(SOURCE_LOCATION_MAP);
+    Stream.EmitRecordWithBlob(SLocMapAbbrev, Record,
+                              Buffer.data(), Buffer.size());
+  }
+
   Abbrev = new BitCodeAbbrev();
   Abbrev->Add(BitCodeAbbrevOp(FILE_SOURCE_LOCATION_OFFSETS));
   Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 16)); // # of slocs
@@ -1591,6 +1593,49 @@ void ASTWriter::WriteSourceManagerBlock(SourceManager &SourceMgr,
   // Write the source location entry preloads array, telling the AST
   // reader which source locations entries it should load eagerly.
   Stream.EmitRecord(SOURCE_LOCATION_PRELOADS, PreloadSLocs);
+
+  // Write the line table. It depends on remapping working, so it must come
+  // after the source location offsets.
+  if (SourceMgr.hasLineTable()) {
+    LineTableInfo &LineTable = SourceMgr.getLineTable();
+
+    Record.clear();
+    // Emit the file names
+    Record.push_back(LineTable.getNumFilenames());
+    for (unsigned I = 0, N = LineTable.getNumFilenames(); I != N; ++I) {
+      // Emit the file name
+      const char *Filename = LineTable.getFilename(I);
+      Filename = adjustFilenameForRelocatablePCH(Filename, isysroot);
+      unsigned FilenameLen = Filename? strlen(Filename) : 0;
+      Record.push_back(FilenameLen);
+      if (FilenameLen)
+        Record.insert(Record.end(), Filename, Filename + FilenameLen);
+    }
+
+    // Emit the line entries
+    for (LineTableInfo::iterator L = LineTable.begin(), LEnd = LineTable.end();
+         L != LEnd; ++L) {
+      // Only emit entries for local files.
+      if (L->first < 0)
+        continue;
+
+      // Emit the file ID
+      Record.push_back(L->first);
+
+      // Emit the line entries
+      Record.push_back(L->second.size());
+      for (std::vector<LineEntry>::iterator LE = L->second.begin(),
+                                         LEEnd = L->second.end();
+           LE != LEEnd; ++LE) {
+        Record.push_back(LE->FileOffset);
+        Record.push_back(LE->LineNo);
+        Record.push_back(LE->FilenameID);
+        Record.push_back((unsigned)LE->FileKind);
+        Record.push_back(LE->IncludeOffset);
+      }
+    }
+    Stream.EmitRecord(SOURCE_MANAGER_LINE_TABLE, Record);
+  }
 }
 
 //===----------------------------------------------------------------------===//
@@ -3926,6 +3971,7 @@ void ASTWriter::ReaderInitialized(ASTReader *Reader) {
          FirstMacroID == NextMacroID &&
          FirstCXXBaseSpecifiersID == NextCXXBaseSpecifiersID &&
          "Setting chain after writing has started.");
+
   Chain = Reader;
 
   FirstDeclID += Chain->getTotalNumDecls();